The present invention relates to a printer and, in particular, to a printer having a paper handling mechanism that reduces paper curling and improves print quality.
Generally, a serial printer operates by moving a recording head in the main scanning direction and feeding paper along a line in a direction perpendicular to the main scanning direction. A paper sheet is fed towards the recording head by a pair of paper feed rollers and is discharged into a stacker by a pair of paper discharge rollers located downstream from the recording head. As the trailing edge (bottom) of a paper is released from the pair of paper feed rollers, the trailing edge is raised towards the recording head as it approaches the nip portion of the pair of paper discharge rollers as a result of the force caused by the weight of the paper being discharged to the stacker. The result is that the size of a gap formed between the recording head and the paper is altered causing the print quality at the bottom of the paper to be adversely affected.
To overcome this problem, Japanese Unexamined Patent Publication No. Hei 7-132658 discloses a technique whereby the paper discharge rollers are inclined toward the recording head so that the trailing edge of the paper is prevented from rising as it is released from the paper feeding rollers.
Typically, in a paper feeding mechanism the rotational speed of the discharge rollers is slightly higher than that of the paper feed rollers so that tension is applied to the portion of the paper that extends between the paper discharge and paper feed rollers. As a result, if the discharge rollers are inclined toward the recording head, as described above, curling of the trailing edge of paper will occur when the tension applied to the paper is released as the trailing edge disengages from the paper feed rollers. Accordingly, it is desirable to provide a printer having a paper handling mechanism that reduces the curling of the paper while maintaining a constant gap size between the recording head and the paper.